Why Your Emergency Generator Won’t Start in the Winter

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So, you’ve been diligent about starting your generator on a regular basis, you’ve kept fuel stabilizer in the tank, and then one cold winter day you go out to fire up your generator and it just won’t start. You might be wondering what you did wrong so let me take a minute and explain what might be going on.

During the 8 plus years that our family lived off the grid our only source of electricity was a generator. Starting certain types of generators in the winter can be a real bear at times. Even our nice Honda EU2000i was often difficult to start during really cold temperatures.

We can’t predict when we’ll need to rely on our emergency generator which is why it’s so important that you read and understand the information in this article.

Why Your Generator Won’t Start When it’s Cold

When the temperature is low, the oil in your generator is going to be cold as well. When oil is cold, it is much thicker than when it is warm. This can cause three problems for you when you’re trying to start a generator on a cold winter morning.

The first is that because the oil is cold and thick, it’s going to be more difficult to pull the cord to start the engine. If it’s normally quite easy to pull the cord, when the temperatures are really low, it’s going to be more difficult because the oil is much thicker.

Cold oil also makes a generator with an electric starter more difficult to start. Cold batteries don’t have as much cranking power. Also keep in mind that just like it’s more difficult for you to pull the cord, the starter on your electric start generator is going to have to work that much harder to crank the engine over. In some cases, you might run the battery down to a level that is so low that it won’t turn the engine over at all.

The third problem that you might experience may seem quite strange to you but keep reading and it will become perfectly clear. Many generators have what are called, “low oil shutdown sensors” on them. These sensors are designed to automatically turn the engine on your generator off if it doesn’t detect that there is enough oil in your generator. This is a GOOD thing because it may help prevent costly engine damage if you don’t have enough oil in your generator’s engine.

Unfortunately, this feature can be very frustrating when the temperatures are cold. Here’s what we experienced with our little Honda generator in sub-freezing temperatures. The generator would start like normal but it might only run for about 10 seconds and then then the low oil shutdown indicator light would illuminate and the generator would automatically shut down.

We were certain that the engine had enough oil in it but the failsafe still triggered. After waiting a few seconds, we would try starting the engine again. If we were lucky, the engine might run for around 15 or so seconds this time before it shut down. Depending on exactly how cold it was, we might have to repeat this process several times. Each time the engine would stay running a little longer than the time before. Eventually, the engine would start and continue running.

Now, keep in mind that we’re not small engine mechanics but since this only happens to us when the temperatures are low, I think it’s fair to believe that since the engine oil is cold and thick, the oil in the generator’s engine isn’t flowing like it would when it is warm. We believe that this is what causes the the low oil shut down sensor to shut the engine off even though the engine isn’t actually low on oil.

Furthermore, this leads us to believe that each time the engine starts and runs for a few seconds the oil is slowly warming up. As it slowly becomes warmer and warmer, it is able to flow more easily. When it flows well enough, the low oil shutdown sensor no longer thinks that there isn’t oil in the engine and consequently, it doesn’t shut the engine down.

I should point out that we’ve owned three of these generators over about 13 years and the reason we kept buying them is because we really like them. We’re actually still using two of the three. My son and daughter-in-law are using one right now as their only source of electricity in our little off-the-grid cabin as a matter of fact.

I would like to point out that we experienced the same symptom on all three generators during cold weather conditions. The solution for us was to consult the owner’s manual to find out what viscosity of oil we should be running in the engine for the current temperatures. The manual said that when the temperatures fell and stayed below a certain temperature, we could use 5W-30 oil which is what we did.

If you choose to change to a lighter weight oil during the winter, be sure to change back to oil of the appropriate viscosity when the temperatures rise to prevent unnecessary engine wear.

Using the proper viscosity oil and following the manufacturer’s instructions for cold weather starts is a much better alternative than restarting the engine over and over until the oil warms up enough for the engine to stay running. If the oil isn’t flowing well enough to keep the sensor from shutting the generator down, it’s not flowing well enough to properly lubricate the engine.

With that in mind, if you find yourself in an emergency and you’re having a difficult time starting your generator because it’s really cold outside. Doing what we did may help you get it started and keep it running. But be forewarned, it very well could extra wear and tear on your generator’s engine.

When we switched to this lower viscosity oil, the problem would sometimes still rear its ugly head to some degree but the generators were much easier to start. So the moral of this story is to read your instruction manual. You just might find that they will recommend that you use oil with a lower viscosity during extremely cold temperatures.

Again, keeping in mind that I’m not a mechanic, it stands to reason that oil that will flow at lower temperatures will do a better job of properly lubricating your generator’s engine on cold days. So, you’ll get a two-fold benefit for making sure that you have the proper oil in your generator during the winter. First, it should be easier to start and second, it may reduce the wear that your engine experiences during cold morning starts.

Read the Manual BEFORE Using Your Generator

I know, I know, reading instruction manuals isn’t much fun but they do contain very important operating and safety information. You might find that the manual for the engine on your generator has special instructions for starting a cold engine and/or running your generator in cold temperatures. So, for your own sanity and in the interest of taking good care of your generator, please read the manual.

More Generator Help Articles

If you’re interested in learning more about generators or you need help with yours click here to see my full list of articles about generators.

Don’t Forget to Read the Comments Below for More Insight

Several people have offered their advice in the comment section below for what they do to help with the problem of starting a cold generator. You might want to read their comments and if you have any tips of your own, please feel free to leave a comment as well.

Off-grid and same issue here, below about 15 degrees F the Honda engine in our whole house generator would only run a few seconds before shutting down with the low oil LED lit. I switched to full synthetic 5w-30 oil and that helped, now it reliably starts down to about 0 degrees.

For the few occasions the temp falls below 0 for an extended amount of time I semi-permanently attached 2 magnetic block heaters ($25-$50 each) with cable ties to secure them and the power cords inside the generator enclosure, and have a spare 1kW gennie kept in the basement where it stays warm. It’s a PITA, but will take the small gennie outside and set it next to the big gennie to power the block heaters for a couple hours before starting the whole house gennie. The low oil shutdown is a safety feature to prevent engine damage, wouldn’t recommend trying to restart the gennie repeatedly until you’ve corrected the problem by warming the oil enough so it can flow.

Yes, I agree that restarting the engine over and over until the oil in the engine is warm enough to flow will most likely cause extra wear and tear on your generator’s engine. Having said that, if someone finds themselves in an emergency and they can’t get their generator started because of cold temperatures, knowing what may be causing the problem could help them to get their generator started. It’s certainly not the ideal solution but I think it’s important to understand that doing this “could” help someone get their generator engine started in an emergency.

Generators are great. We absolutely love our standby generator; and living where we do, we have had many opportunities to appreciate it over the 17+ years since installing it.

Some comments:

Achieving optimum performance from any generator under all conditions, including cold weather, BEGINS with a clear and complete understanding of the information included in the generator Owner’s Manual. Since knowledge is power, and since no generator is inexpensive, empower yourself and protect that investment by arming yourself with essential, readily available knowledge, understanding everything your manual tells you, and complying with the procedures it spells out. And no less importantly, GUARD YOUR SAFETY by complying with all the warnings the Owner’s Manual spells out.

In this small but important way our approaches differ: though you gently and perhaps jokingly suggest “When all else fails, read the manual”, I think you should NOT wait until you have a problem to read the manual; but instead you should thoroughly familiarize yourself with the contents of your Owner’s Manual before you ever employ your generator to provide you with electricity.

Now to the matter of cold generator oil and “Cold Weather Ops”…

Your readers might like to know that one or more types of electric pre-heaters can be employed to keep the oil in many generators warm enough to facilitate the start/run function during cold temperatures and thereby, as you indicate, reduce the wear-and-tear on the engine and extend the life of the generator. Those types of pre-heaters include the following:

-“Dipstick”-style heaters, inserted down into the oil through the oil filler tube.

-“Blanket” or “Heating Pad”-style heaters that wrap around or attach to the bottom of the oil pan on the unit.

-“Engine block”-style heaters that are permanently plugged into the engine block.

-There are even “magnetic”-style heaters that attach magnetically to the oil pan.

Know, too, that simply plugging in any of these electric oil heaters through an inexpensive device such as the “TC3 Cold Weather Thermo Cube” attached to the end of your power supply cord will allow the oil heater to operate only in relatively cold ambient temperatures — between 35F(on) and 45F(off). Configured in this way, the heater is not electrically heating the oil unnecessarily when the ambient temperature is sufficiently warm.

(To learn more about such accessories for your generator, whether yours be a “portable” generator or a “fixed-location standby” generator, do searches on “oil pan heater” and “engine block heater” and “thermo cube”.)

Some important warnings about generators:

ATTENTION! BE WARNED: Whether or not you’re new to the use of generators, every user needs to know, understand, and keep in mind that electricity can be extremely dangerous and can kill you or others, including your loved ones and pets, by means of electrocution and/or fire. And so for that reason, too, once again I urge everyone — in the strongest sense of the word — to READ AND UNDERSTAND THE D*** MANUAL, cover-to-cover, BEFORE ever using your generator. You will find numerous warnings published in it, including some version of the following:

-NEVER attempt to power any electrical circuit — especially in a dwelling or other building — without first physically disconnecting the associated electrical distribution panel from normal street power.

-NEVER attempt to power any electrical circuit — especially in a dwelling or other building — by “back-feeding” the circuitry (e.g., plugging the generator output directly into a wall plug).

Lastly, I fully agree with what you say in another of your previous articles: a “Transfer Switch” — whether manual or automatic — is an important and useful safety and operational component in a standby generator configuration. From our experience it is without question worth the money.

Thanks for your tips! In retrospect, I fully agree with your comment about jokingly suggesting to read the manual. I appreciate your feedback and I’ve modified the article to encourage people to read the manual BEFORE using their generator.

I’m of grid on solar power, in the north where it gets -30F and occasionally need to run the genny too. Your piece is spot on target. If I might offer a small hint — I generally have a pretty good idea when I’ll be running the generator. If it’s cold I drape a tarp over it and put in a propane tent heater. One of those little heaters that has about a 6″ round “plate” on top and you screw in a 1# propane bottle. About an hour and the unit is at 70F or so and starts right up.

Thanks for your kind words. I understand your desire to want to do something to warm the generator before you use it but I would personally not want any kind of a heating device such as a propane heater with a flame anywhere near the fumes that the gas tank on a generator might emit. I would be to afraid of the possibility of starting a fire.

“[I] would personally not want any kind of a heating device such as a propane heater with a flame anywhere near the fumes that the gas tank on a generator might emit.”

I understand your fear of starting a fire from the gasoline fumes. ALL generators should be outside, in the open air. There should be very little chance of a fire, especially if there is ANY kind of a breeze. When the heat source is up-wind of the generator and the fumes are being blown AWAY from the flame of the heater. I would NOT however put a tarp over the generator/heater.

The type of heater John is talking about generally gives off a lot of RADIANT heat and can be a little farther away from the generator and still warm it up. It just takes a little longer. You also don’t need to wait until the generator is up to 70º to try to start. Maybe only 45º to 55º is warm enough to start it.

When I hook up my generator to the electric box, I use a 220/240 volt circuit to “back feed” the power into the house.

The FIRST thing I do is START the generator (or at least ATTEMPT to) to get the generator stabilized.

The SECOND thing I do is to TURN OFF THE MAIN BREAKER, to disconnect the house from the power grid, and TURN OFF ALL THE CIRCUIT BREAKERS. The reason I do that is to not overload the generator with EVERYTHING coming on at the same time. You want to turn on circuits one at a time and only the circuits you NEED!

The THIRD is to connect the cable to the 220/240 volt A/C circuit, since this circuit is outside.

The FORTH is to plug in the cable to the generator.

Then and ONLY THEN do I proceed with step FIVE. Throwing “ON” the breaker that is hooked to the generator to feed power to the house. Then the breakers with any MOTORS (furnace, refrigerator, freezer, etc.) then any other necessary circuits.

When utility power is restored, I disconnect and shut down the generator, THEN THROW THE MAIN POWER BREAKER TO “ON” to supply utility power to the house again.

Are you saying that you back feed the power directly into your house instead of using a generator transfer switch? I’m certainly not an electrician but I believe that a properly wired transfer switch should be used to help prevent any possible injury to the electric company technicians while they are working on the lines to restore power.

A transfer switch commonly referred too as a double pole double throw switch or a mechanical interlock are required by the National Electrical Code for portable generators too prevent back feed into the grid and hurting someone or even electrocution why not do it right?? think about what can happen too you if you do something wrong and someone gets hurt because of your stupidity.